Die for tube reducing



1943- ;J. B. TIEDEMANN 2,328,112

DIE FOR TUBE REDUCING Filed Jan. 28, 1941 INVENTOR.

ATTORNEY i Patented Aug. 31, 1943 DIE FOR TUBE REDUCING Julius B. Tiedemann, Milwaukee, Wis., asslg'nor to A. 0. Smith Corporation, Milwaukee, Wis., a corporation of New York Application January 28, 1941, Serial No. 376,347

I Claims. This invention relates to dies for reducing the diameter of tubes orpipes.

Swaging machines are frequently used to apply dies to the exterior of a tube or pipe and reduce its diameter in relatively short increments of length. One example of such a machine is shown in my co-pending application for patent, Serial No. 276,046, filed May 27, 1939, which has matured into Patent No. 2,247,863, of July 1, 1941.

In such machines, two or more external dies are applied to the tube or pipe, roll upon it for a distance to reduce the diameter of a relatively short increment of length, and then recede from it to permit the tube to be rotated andfed forward in readiness for another stroke.

viding machines of this type with dies which are of long life, and which reduce the diameter of the tube being operated upon without producing folds or flaws in the metal or objectionable variations in the wall thickness of the reduced tube. This problem is particularlyserious when it is desired to operate without an internal mandrel to support the tube and assist in the maintenance of uniform wall thickness and internal diameter.

One of the objects of the invention is to provide improved dies for us on machines of this character. I

Another object of the invention is to provide dies of such contour that they can be employed to reduce the diameter of either hot or cold tubes without requiring the use of an internal mandrel.

A further object of the' invention is to provide an improved die construction which permits the dies to be readily and cheaplyi'emachined and restored for further use after they are worn.

These and other objects of the invention will be clear from the following detailed description and drawing illustrating an embodiment of the invention.

Inthe drawing:

Figure 1 is a side elevation of the dies with a tube between them;

Fig. 2 is an end ele ation of the dies looking from the left hand side in Fig. 1;

Figs. 3 and 4 are enlarged fragmentary views showin the shape of the opening between the dies at different positions, the sections through the die being on a plane transverse to the axis of the pipe which the dies act upon;

Fig. 5 is a'cliagrammatic view somewhat exagpipe; and

- A problem which often arises is that of proremachined and restored for further use after having been enlarged by wear.

Referring to the drawing, and in particular to Figf 1, two substantially identical dies 1 are shown, one'aboveand one below the tube 2 which is being reduced in diameter between tb em. The

dies are supported in and'actuated by a suitable swaging machine whichforms no part of this invention and is not shown in the drawing. The action of such machine is to .close the dies upon the tube 2 and then roll them along it, after which the dies are lifted and the tube is fedforward (from left to right in Fig. '1) and turned on its axis to be in readiness for another stroke.

,The dies may first b closed upon the small or reduced end of the pipe and then rolled up the taper from the reduced to the unreduced portion Figs. 6 and 7 are diagrammatic sections illustrative of the ease with which the dies can be from being carried along with the tube.

of the tube; or alternatively, the dies may first be closed on the unreduced portion of the tube and rolled down the taper.

For the hot reduction of'tubes, which come from a furnace, covered with scale, there are some advantages to be gained by rolling up .the taper. The dies rolling from the small to the large diameter loosen the scale, and jets can be directed opposite the forward motion of the tube to blow the scale back towards the furnace and keep it In view of this advantage it may be preferred to operate the diesso as to roll up the taper, but the opposite procedure can be used if other considerations direct its choice.

In view of the rolling action of the dies, their meetin edges 3 are curved to approximate a segment of a circle of considerable radius. This radius will be referred to as the radius of the dies, and may varyweight of metal needed, and with bolt holes 1 to attach the dies to the die supports in the swaging machine. Bearing surfaces 8, 9 and Ill on the die halves may be machined and serve to transfer pressure from the dies to the swaging machine and facilitate accurat adjustment of the position The of the dies in the support. For reasons to be explained hereinafter, it is preferred to slightly space the dies apart by means of a shim ll! finished off flush with the die surfaces.

Three important factors are involved in the production of satisfactory dies, namely, the radius of the dies as defined above; the degree of taper produced on the pipe between the reduced and unreduced portions; and the shape of the opening between the dies.

The die radius should be large compared to the radius of the pipe being reduced. If the meeting edges 3 of the dies are at a distance equal to R from the instantaneous center of die rotation,

then the parts of the dies in contact with the uppermost and lowermost parts of the pipe in Fig. 1 will be a distance substantially equal to R minus r from the center of instantaneous rotation, r being the radius of the pipe. This expression would be exact if the meeting edges of the dies actually came in contact on a plane through the center line of the pipe, and will be substantially correct if the meeting edges are slightly spaced as indicated in the figures.

Due to this difference in distance from the center of rotation, any rotation of the die will necessarily bring about a slippage between some points of the die and th points on the pipe with which they are in contact. This slippage will be less the greater the ratio of die diameter to pipe diameter. As a decrease in slippage contributes to both better quality of product and longer die life, the radius of the dies is preferably chosen as large in comparison with the pipe radius as is consistent with a machine of reasonable size.

A smaller ratio than that shown in the drawing can be used with'entirely satisfactory results and might well be employed for work on larger diameter pipe to avoid the use of dies and machines of too great size. For smaller pipe, on the other hand, an even greater ratio could be employed without necessitating the use of too bulky dies or machines.

The opening between the dies tapers from a size at one end sufilcient to receive the incoming pipe to an opening at the other end having the size of the reduced pipe. the size of the die opening determines the taper produced on the pipe between the reduced and unreduced portions. The steeper the taper, the shorter the tapered section of thedies can be for a given reduction in diameter. It has been found, however, that too steep a taper is not conducive of the best results and it is preferred to so shape the dies that the taper on the pipe does not exceed about 15 as measured from one side of the pipe to the center line. Excellent results have been obtained with dies which produc a substantially uniform taper from one end of the tapered section to the other, but it is not essential that.the taper be uniform provided that it is nowhere too steep.

The shape of the die opening in a plane transverse to the pipe axis is of great importance. If this is made round so that the opening in the tapered portions of each die is substantially semicircular, it is found that near the meeting edges of the die, the die scrapes upon and pinches the pipe as it closes on it. This has an undesirable effect upon the properties of the pipe or tube produced, and also results in serious wear on the die which increases the horizontal diameter of the opening.

In the improved dies of this invention the opening in the tapered section of the die is made oval The rate of change in with the short axis in the line along which the dies approach each other as they close upon the pipe. at its mid point uniting two circular arcs I4 and i5. In some instances it may be desired to have the dies close together on a plane through the axis of the pipe, in which case each of the arcs l4 and I5 will be a complete quadrant of a circle. In other instances, the closest approach of the dies towards each other i controlled by the swagin machine in which they ar mounted rather than by mutual contact of the dies, and in this case clearance I! is provided so that each of the arcs M and I5 falls slightly short of being a complete quadrant.

When the dies separate, the pipe is fed forward and also rotated on its axis through one quarter turn. The previous closure of the dies will have flattened the part of the pipe in the tapered portion of the dies into an oval section with its major axis horizontal. When the pipe is turned through an angleof in readiness for the next strokeof the dies, the major axis of the oval section on the pipe will be vertical.

It is a characteristic of the dies 0f.this invention that the minor axis of the oval die opening at any position on the tapered section is made substantially equal to the major axis of the oval opening at a position nearer the exit of the dies by an amount equal to the feed imparted to the pipe between successive strokes of the dies, as shown in Fig. in which the oval shape of the pipe 2 and dies i has been exaggerated for the purpose of illustration.

When the dies are made in this way, the horizontal axis of the oval pipe section ready for the next stroke of the dies, is at every point along the tapered portion of the dies substantially equal to the horizontal axis-of the die opening. The dies can therefore close by vertical motion without pinching the pipe along the meeting edges of the dies, or without excessive wear on the portioris of the dies indicated at l2. Contact is first established between the pipe and dies at points l8 and I9, and as the dies close they compress the pipe between them.

If the pipe is fed forward between stroks a lesser amount than the feed for which the dies are designed, favorable conditions for the closing of the dies are still maintained but the production from the machine will be decreased due to the lesser feed. If the feed given to the pipe is greater than the feed for which the dies are designed, conditions are less favorable for the closing of the dies, die wear is increased, and less satisfactory pipe is produced.

After the pipe or tube has been reduced in diameter in the tapered section of the dies, the reduced pipe is acted upon by the straight portion of the dies. As no further reduction is accomplished here 'and this portion of the die is simply to round and straighten the reduced pipe, the die opening is made circular as previously explained.

Dies made in accordance with this invention have operated satisfactorily and with a long life on both hot and cold reduction of tubes. Such die wear as does occur is fairly uniformly distributed over the surface of the dies instead of beingconcentrated in one or more places as was frequently the case with prior dies.

While each of the two dies can be made in a single piece, it is preferred to make them in halves. The working face of each die half 4 and 5 is then finished to theform of substantially a quadrant of a circular arc and theflat portion in Each die has a substantially fiat section i3 the major axis of the oval die opening is provided by the shim H placed between the halves. Wear on the dies increases the major axis of theoval die opening somewhat faster than the minor axis. When the die opening has been enlarged by wear to an undesirable extent, the shim II is removed and replaced by a thinner shim, thus decreasing the major axis of the die opening. The dies are hence restored for further use without the necessity for regrinding or remachining the working surface.

Further wear on the dies ultimately makes it necessary to regrind or remachine the working surface. Construction of the dies in two halves is also an advantage here in reducing the amount of metal that must be removed to reshape the dies for further use. Referring to Fig. 67in which the wear is shown greatly exaggerated for the purpose of illustration, consider a single piece die in which the oval die opening was originally as shown at 2'. and was subsequently enlarged by wear to the shape shown at 2!. Refinishing the die to produce an opening of the original dimensions will require the removal of metal in the shaded areas 22, 23, and 24. The removal of this metal involves considerable expense, and is further objectionable in that it reduces the size of the die and makes it possible to refinish it only a limited number of times before the die must be scrapped.

Consider now half of a die made in two pieces ber of times before they must be scrapped.

I claim:

1. A die for reducing the diameter of a tube in a swaging machine of the kind in which the tube is rotated on' its axis through substantially one quarter of a turn and fed forward to the machine between successive strokes of the dies, said die having a working surface defining an opening tapering longitudinally of the die, the section of the opening transverse to the tube axis being substantially half an oval with the minoraxis of the oval in the directionof die closure on the tube,

and with the minor axis of the oval at any longitudinal position on the the equal to the major axis of the oval at a position nearer the small end of the tapered opening by an amount not less than the feed imparted to the tube between strokes of the dies.

2. A die for reducing the diameter of a tube in a swaging machine of the kind in which the tube is rotated on its axis through substantially one quarter of a turn and fed forward to the-machine between successive strokes of the dies, said die having a working surface which defines an opening tapering longitudinally of the die from a mating the size of reduced tubing the die is to produce, the opening tapering gradually from end to end to form between the reduced and unreduced sections of the tube a tapered section on the tube with a taper which is at no point greater than about one and one-half degrees measured from one side of the tube to its axis, the section of the tapered opening transverse to the tube axis being substantially half an oval with the minor axis of the oval in the direction of die closure on the tube.

3. A die for reducing the diameter of a tube in a swaging machine of the kind in which the tube is rotated on its axis through substantially one quarter of a turn and fed forward to the machine between successive strokes of the dies, said die having a working-surface which defines an opening tapering longitudinally of the die from a size at one end sufficient to accommodate an unreduced tube to a size at the other end approximating the size of reduced tubing the die is to pro duce, the opening tapering gradually from end to end to form between the reduced and unreduced sections of the tube a tapered section on the tube with a taper which is at no point greater than about one and one-half degrees measured from one side of the tube to its axis, the section of the tapered opening transverse to'the tube axis being substantially half an bval with the minor axis of the oval in the direction of die closure on the tube, and with the minor axis of the oval at any longitudinal position on the die equal to the major axis of the oval at a po-' sition nearer the small end of the tapered opening by an amount not less than the feed imparted'to the tube between strokes of the dies.

4. A two piece die for reducing the diameter of a tube in a swaging machine of the kind in which the tube is rotated on its axis through substantially one quarter of a turn and fed forward to the machine between successive strokes of the dies, said die having a working surface which defines an opening tapering longitudinally of the die from a size at one end suflicient to accommodate an unreduced tube to a size at the other end approximating the size of reduced tubing the die is .to produce, and being separable into two pieces substantially along the median line of the working surface, the section of the tapered opening transverse to the tube axis being substantially half an oval with the minor axis of the oval in the direction of die closure on the tube and with the minor axis of the oval-at any longi;

spaced from each other by removable longitudinal shimming material to prevent excessive re grinding and remachining of the dies after wear, each of said sections having its die surface machined on an arc-of a circle, and said shimming material providing the additional width of the die cavity.

, JULIUS B. TIEDEMAN'N. 

